In order to understand the spatial distribution and the pollution source of total nitrogen, total phosphorus and ammonia nitrogen in Datong Lake, samples were collected on September, 2017, from Datong Lake and its surrounding rivers. The results showed that: The total nitrogen concentration of the rivers around Datong Lake ranged from 0.74 to 2.18 mg/L, the ammonia nitrogen concentration ranged from 0.094 to 0.874 mg/L, and the total phosphorus concentration ranged from 0.02 to 0.243 mg/L. As for the lake body, the total nitrogen concentration ranged from 0.82 to 1.47 mg/L, exhibiting the characteristics of lower in the center but higher in surrounding areas in the lake body. The concentration of ammonia nitrogen ranged from 0.14 to 0.42 mg/L, but the overall difference was relatively large. The high value areas were mainly in the southwest and east of Datong Lake. The total phosphorus concentration ranged from 0.160 to 0.289 mg/L, so the water quality was classified as class V or inferior class V. The total phosphorus was the main pollutant in the lake body, which showed an increasing trend from the surrounding to the middle, and the high concentration areas were mainly concentrated in the south and middle of Datong Lake. According to the statistics of pollution sources of Datong Lake in 2016 and the calculation of pollutants discharged into the lake, the order of total phosphorus pollution load of Datong Lake is farmland runoff >livestock breeding >domestic sewage > industrial pollution > net cage fish culture > tourism services.